The monitoring network within this area

Hydrionis holds 1,469 values from 6 gauges within it. Discharge is a property of a gauge and its reach, not of this drainage area, so this page reports the network and its records rather than a single figure.

Gauges

1,469

Values held

1924–2026

Record spans

Gauges within the Upper Dan huc8 subbasin

6 monitoring points, positioned as the publisher records them.

Flood peaks, as measured

This gauge's flood record, as measured. Unlike a daily mean it is the discharge at the moment the river was highest, which is the figure flood frequency analysis is built on.

Largest measured flow of each year at NORTH MAYO RIVER NEAR SPENCER, VA

The highest instantaneous discharge the publisher recorded in each year — a flood peak as measured, not a daily average of one. 1929–2025.

Show relevant events (1 event)Shading marks when something was recorded, not what caused the line.

Published by the gauge's own operator from its sub-daily record; Hydrionis stores the figure rather than recomputing it. A year the gauge did not cover produces no value rather than a low one, and the gaps are stated below the chart. A peak is a property of this gauge and its reach: a larger flood upstream or downstream of it is not in this series.

What the shaded periods are (1 event)

A shaded period marks when something was recorded, not what caused the shape of the line. Where the two coincide, they coincided.

Documented record — A documented event, compiled from cited sources after it happened. The dates are as good as the record, which for older events can mean the month rather than the day.

Event	Type	Period	Standing	Authority
Hurricane Katrina water and sanitation collapse	Flood	2005-08-29 – 2005-09-30	Documented record	Compiled record

Not shown on this chart

The 1976 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
The 2022 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Yorkshire drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Cantareira water crisis, São Paulo — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Cape Town Day Zero — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
European drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.

View the data behind this chart

Underlying data
Period	NORTH MAYO RIVER NEAR SPENCER, VA (m³/s)
1929	47.0
1931	56.1
1932	80.4
1934	41.1
1935	37.1
1936	90.6
1937	86.6
1939	108
1940	193
1942	141
1943	75.3
1944	73.1
1945	206
1946	52.4
1947	41.9
1949	70.8
1950	39.4
1951	47.6
1953	70.8
1954	62.3
1956	47.6
1957	180
1958	89.2
1959	127
1961	53.0
1963	84.4
1964	70.8
1965	64.3
1966	64.3
1967	37.1
1968	53.0
1970	70.8
1972	357
1973	77.6
1974	96.8
1975	99.7
1976	41.3
1978	94.3
1979	371
1980	114
1981	21.1
1983	90.9
1984	54.4
1985	399
1987	354
1989	195
1990	113
1992	161
1993	114
1994	79.9
1995	79.0
1996	167
1997	70.5
1998	75.0
1999	32.8
2000	30.3
2001	37.9
2002	29.7
2003	149
2004	101
2005	56.6
2007	69.7
2008	90.6
2009	79.6
2010	223
2011	58.9
2013	74.2
2014	41.9
2015	158
2017	83.3
2018	165
2020	235
2022	64.0
2023	67.4
2024	133
2025	37.9

About this series

Everything below is a property of the data rather than a rating of it. There is deliberately no single confidence score: how much a gap matters depends on what you are about to do with the series, and only you know that.

Source	United States Geological Survey — National Water Information System · US Government work — public domain
How the values came to exist	Measured
Period held	1929–2025
Completeness	78.4% of the periods in that span are held. Gaps are drawn as breaks and never interpolated.
Known gaps	21 separate periods inside 1929–2025 hold no value. They are drawn as breaks in the line and are never interpolated across.
Continuity	The record begins in 1929 and is not continuous from it: 97 years separate the first value from the last, and 78% of the years between them are held. The span is not the record.
Last read from the publisher	2026-10-01
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced

How much of the rain came back out

A discharge in cubic metres per second cannot be compared with anything: the larger number may only mean the larger catchment. Divided by the area draining to the gauge it becomes a depth of water over that land, which answers a question a reader already has — of the rain that fell here, how much came back out as river?

Water leaving the catchment above SANDY RIVER NEAR DANVILLE, VA, as a depth

The year's flow spread over the land draining to this gauge, in millimetres — the same unit rainfall is measured in. 1930–2024.

Show relevant events (1 event)Shading marks when something was recorded, not what caused the line.

Computed by Hydrionis from the published annual mean flow and the catchment area the station's own publisher states. It is not a water balance: the difference between rainfall and runoff is not evaporation alone but also change in groundwater storage, water abstracted and taken elsewhere, and water imported by transfer schemes — which is why a catchment can yield more runoff than the rain that fell on it without anything being measured wrongly. A different area figure rescales every value here by the ratio between them.

What the shaded periods are (1 event)

A shaded period marks when something was recorded, not what caused the shape of the line. Where the two coincide, they coincided.

Documented record — A documented event, compiled from cited sources after it happened. The dates are as good as the record, which for older events can mean the month rather than the day.

Event	Type	Period	Standing	Authority
Hurricane Katrina water and sanitation collapse	Flood	2005-08-29 – 2005-09-30	Documented record	Compiled record

Not shown on this chart

The 1976 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
The 2022 drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Yorkshire drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Cantareira water crisis, São Paulo — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
Cape Town Day Zero — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.
European drought — This event’s area does not contain this chart’s subject. Sharing a country is not sharing an event, so it is not drawn.

View the data behind this chart

Underlying data
Period	SANDY RIVER NEAR DANVILLE, VA (mm)
1930	184
1931	206
1932	266
1933	202
1934	337
1935	299
1936	461
1937	514
1938	320
1939	325
1940	388
1941	235
1942	255
1943	271
1944	455
1945	334
1946	295
1947	331
1948	407
1949	372
1950	288
1951	251
1952	313
1953	230
1954	292
1955	298
1956	276
1957	366
1958	427
1959	295
1960	400
1961	392
1962	369
1963	277
1964	306
1965	279
1966	233
1967	262
1968	226
1969	239
1970	258
1971	380
1972	539
1973	464
1974	362
1975	559
1976	291
1977	231
1978	516
1979	586
1980	319
1981	175
1982	292
1983	375
1984	441
1985	348
1986	186
1987	499
1988	226
1989	479
1990	540
1991	372
1992	277
1993	462
1994	340
1995	386
1996	618
1997	333
1998	462
1999	252
2000	243
2001	189
2002	201
2003	564
2004	421
2005	351
2006	262
2007	283
2008	221
2009	354
2010	330
2011	183
2012	159
2013	299
2014	257
2015	332
2016	425
2017	315
2018	566
2019	444
2020	579
2021	345
2022	220
2023	304
2024	301

About this series

Source	United States Geological Survey — National Water Information System · US Government work — public domain
How the values came to exist	Derived Computed by Hydrionis
Period held	1930–2024
Completeness	100.0% of the periods in that span are held.
Continuity	Continuous: every year from 1930 to 2024 is held.
Inputs last read	2026-10-01 · when the records this was computed from were last read from their publishers
Calculation date	2026-08-24 · when the calculation method was last versioned, not a reading of any publisher
Redistribution	Permitted by the upstream licences
Commercial reuse	Permitted by the upstream licences. No Hydrionis access tier can widen this.
Methodology	How this was produced

Every gauge Hydrionis holds within this area

Gauges within the Upper Dan and what each holds
Gauge	Measures	Values	Record
NORTH MAYO RIVER NEAR SPENCER, VA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	323	1928–2026
DAN RIVER NEAR FRANCISCO, NC	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	297	1924–2026
SANDY RIVER NEAR DANVILLE, VA	catchment area, annual maximum river flow, mean river flow, mean river flow, water year	287	1929–2026
SMITH RIVER AT MARTINSVILLE, VA	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	282	1929–2026
MAYO RIVER NEAR PRICE, NC	burned area within 50 km, catchment area, annual maximum river flow, mean river flow, mean river flow, water year	259	1929–2026
DAN RIVER AT PINE HALL, NC	catchment area, annual maximum river flow	21	1987–2026

How these gauges were attached to this water

Assigned by the publisher to a numbered basin Every gauge here is assigned to this drainage area by its own publisher, which issues the area an official code — 03010103. A drainage area is not a river: it contains the tributaries as well as the main channel, and a gauge in it may be on any of them.

What each gauge’s link to this water rests on
Gauge	Evidence	Established
NORTH MAYO RIVER NEAR SPENCER, VA	Stated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/4	2026-10-02
DAN RIVER NEAR FRANCISCO, NC	Stated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/4	2026-10-02
SANDY RIVER NEAR DANVILLE, VA	Stated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/4	2026-10-02
SMITH RIVER AT MARTINSVILLE, VA	Stated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/4	2026-10-02
MAYO RIVER NEAR PRICE, NC	Stated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/4	2026-10-02
DAN RIVER AT PINE HALL, NC	Stated by the publisher — USGS site service, huc_cd field — https://waterservices.usgs.gov/nwis/site/ ; named from the USGS Watershed Boundary Dataset 8-digit HU (Subbasin) layer — https://hydro.nationalmap.gov/arcgis/rest/services/wbd/MapServer/4	2026-10-02

What this record holds

Hydrionis decides which waters get a page, and which of those are offered to search, from what is actually held rather than from how the page reads. Five signals are counted; this record has 5 of them, which makes it a full profile.

Information-gain signals held for this water body
Signal	Held	Counts
Gauges holding a real record	5	yes, 3 or more
Years spanned	103	yes, 20 or more
Values held	1,469	yes, 1000 or more
Distinct measurements	5	yes, 2 or more
Publishers measuring it	2	yes, 2 or more
Official identifiers	1	recorded, not counted

Use this data

Machine-readable JSON /api/v1/observations/by-subject/gauge-usgs-02070000.json
How to cite this, and who you must credit
How these figures were produced
Request this at a different scale, format or geography

No bulk download is offered here, which is a licence position rather than a product one: at least one contributing publisher does not permit redistribution. The values can be read on the page, cited, and pointed to at source.

Attribution and citation

Suggested citation for Hydrionis

Hydrionis (2026), Upper Dan gauge records, accessed 2026-10-05, hydrionis.com/waters/united-states-upper-dan/

Cite Hydrionis where you rely on values Hydrionis computed, on the method that produced them, or on the compilation itself. The underlying measurements remain the publishers’ and their attribution requirements apply to you directly.

Recommended, not required. Hydrionis does not claim rights over unmodified public data it relayed, and doing arithmetic on somebody else’s measurements does not make them Hydrionis’s. Cite the version and the access date: the Upper Dan gauge records changes as publishers release and as methods are revised, and a citation without both cannot be checked later. Full guidance is on cite and reuse.

None of the contributing licences requires attribution. Crediting the publishers is still good practice and they are listed above.

Where these figures come from

MeasuredHigh confidence2025-02-13

Source: USGS — National Water Information System, USGS site 02070000, annual peak streamflow. Licence: Open.

Method: The instantaneous maximum discharge of each water year as published by USGS, dated to the day it occurred. One value per October-to-September water year; where the publisher lists both a systematic and a historic peak for a year, the larger is the annual maximum. Values the publisher marks as maximum daily averages are not held here, because they are not instantaneous peaks. Values marked as bounded rather than measured are held as censored observations carrying the bound. Cubic feet per second are converted to cubic metres per second and the publisher unit is recorded alongside.

Rating curves are extrapolated at extreme discharges, so the largest values in a peak series carry the largest measurement uncertainty. Data from the U.S. Geological Survey National Water Information System, a work of the United States government and therefore in the public domain.

Retrieved 1 October 2026.